Chapter 17 - A coupled anisotropic damage model for the inelastic response of composite materials

Abstract

This chapter introduces a coupled incremental damage and plasticity theory for rate independent and rate dependent composite materials. This theory allows damage to be path dependent either on the stress history or thermodynamic force conjugate to damage, which is achieved through the use of an incremental damage tensor. Damage and inelastic deformations are incorporated in the proposed model that is used for the analysis of fiber-reinforced metal matrix composite materials. The damage is described kinematically in both the elastic and inelastic domains using the fourth order damage effect tensor, which is a function of the second-order damage tensor. A physical interpretation of the second order damage tensor is presented, which relates to the microcrack porosity within the unit cell. The inelastic deformation behavior with damage is presented here within the framework of thermodynamics with internal state variables. Computational aspects of both the rate independent and rate dependent models are also discussed in the chapter. The Newthon Rapson iterative scheme is used for the overall laminate system. To test the validity of the model, a series of laminated systems (0(8s)), (90(8s)), (0/90)(4s), and (-45/45)(2s) are investigated at both room and elevated temperatures of 538° C and 649° C. The results obtained from the special purpose developed computer program, DVPCALSET(Damage and Viscoplastic Coupled Analysis of Laminate Systems at Elevated Temperatures), are then compared with the available experimental results and other existing theoretical material models.